Microstructure and magnetocaloric property of homogeneous La (FexSi1-x)13 compounds fabricated by laser fusion using a powder mixture of Fe and LaySiz compounds

A highly homogeneous single-phase La(FexSi1-x)(13) was obtained by the heat-treatment of a parent alloy produced by the laser fusion of a powder mixture of Fe and La-Si compounds. Rapid homogenization was promoted owing to the formation of a characteristic microstructure during laser fusion even at a high Fe concentration (e.g., x = 0.91). The selective oxidation of La during laser fusion was prevented by the reduction of oxides on the surface of Fe particles. The maximum of the magnetic entropy change (Delta S-M) for the specimen heat-treated at 1323 K for 24 h was - 22 J/kg K under a magnetic field change of 1 T and the specimen heat-treated for a shorter duration of 2 h exhibited a Delta S-M of - 18 J/kg K. Thus, the production of the parent alloy by the laser fusion of the powder mixture significantly decreased the heat-treatment duration for the formation of a highly homogenized La(FexSi1-x)(13) compound at a high Fe concentration. Consequently, the laser fusion process followed by post-annealing is possible to selectively form fine structures made of the 1:13 phase, and such a feature will lead a way to 3D precision modeling of the regenerator-bed with using the highly homogeneous La(FexSi1-x)(13). (C) 2022 Published by Elsevier B.V.

Automated summary

A highly homogeneous single-phase La(FexSi1-x)(13) compound was successfully obtained by the laser fusion of Fe and La-Si compounds. Rapid homogenization was achieved even at high Fe concentration due to the formation of a unique microstructure during laser fusion. The selective oxidation of La was prevented by reducing oxides on the surface of Fe particles. The heat-treated specimens exhibited a maximum magnetic entropy change (ΔS-M) of -22 J/kg K for the 24-hour treatment and -18 J/kg K for the 2-hour treatment. The laser fusion process significantly reduced the heat-treatment duration for the formation of a highly homogenized La(FexSi1-x)(13) compound. This study suggests that the laser fusion process followed by post-annealing can selectively form fine structures made of the 1:13 phase, enabling precise modeling of regenerator-beds in 3D.